German has two common words for “because”: weil and denn. They mean almost the same thing, but they behave differently in a sentence, and that is what catches learners out.

The one rule

Denn is a coordinating conjunction: it joins two main clauses, and the word order of each stays exactly as it would be on its own. Weil is a subordinating conjunction: it starts a subordinate clause, and the conjugated verb moves to the end.

Ich bleibe zu Hause, denn ich bin krank.

I’m staying at home because I’m ill.

Ich bleibe zu Hause, weil ich krank bin.

I’m staying at home because I’m ill.

Look at the end of each sentence. After denn it is ich bin krank, with the verb second. After weil it is ich krank bin, with the verb last.

Weil: the verb goes last

Whatever else is in the clause, the conjugated verb ends up at the very end. With the perfect tense or a modal verb, that means the whole verb group moves back, and the conjugated part comes last:

Sie ist müde, weil sie lange gearbeitet hat.

She is tired because she worked for a long time.

Er kommt nicht, weil er arbeiten muss.

He isn’t coming because he has to work.

A separable verb joins up again at the end. Compare Ich stehe früh auf with …, weil ich früh aufstehe.

Denn: nothing changes

After denn, carry on as if you had started a new sentence:

Er ist glücklich, denn er hat die Prüfung bestanden.

He is happy, because he passed the exam.

Denn always sits between the two clauses, after a comma. Unlike weil, it cannot start a sentence that then turns round to the main clause.

Which should you use?

In meaning they are very close, so either is usually fine. Some differences are worth knowing:

  • Weil is more flexible. It can answer a question that starts with warum: Warum kommst du nicht? Weil ich krank bin. Denn cannot.
  • Weil can come first. Weil ich krank bin, bleibe ich zu Hause. Note bleibe ich: after a clause at the start, the main clause begins with its verb.
  • Denn is often used more in writing. It gives a reason as an extra explanation, where weil ties the reason more closely to the statement.
  • In everyday speech many Germans use weil with the verb in second place (weil ich bin krank). You will hear it, but in writing and exams the verb belongs at the end.

There is also a small word denn that adds a note of interest to a question, as in Was ist denn das? (“What is that, then?”). It is a different use and has nothing to do with “because”.